For example, a free float steam trap disclosed in Japanese unexamined patent publication No. 55-135292 is provided with a spherical float itself which rises due to buoyancy and descends in a free state in a valve chest and also has a function of valve body. The steam trap of this type is provided with a single operating portion in comparison with a conventional steam trap in which a float, a level and a valve body are individually separate, and its structure is extremely simple, so that there occurs little trouble. Furthermore, since the entire surface of its float valve put in a free state forms a seal surface, a new valve surface can be easily obtained relative to a valve seat.
The construction of the conventional free float steam trap is shown in FIG. 7. A trap casing is constituted by attaching a cover member 93 to a main body 90 having an inlet port 91 and an outlet port 92. A valve chest 94 is formed in the interior portion thereof. A float valve 95 is accommodated in a free state in the valve chest 94. A valve seat member 96 is mounted on a lower portion of the valve chest 94 and held by a plug 97. At the valve seat member 96 is formed a valve orifice 98 opened to the valve chest 94. The valve orifice 98 communicates with the outlet port 92 through an outlet passage 99. Condensate entering from the inlet port 91 stays in the valve chest 94. The float valve 95 rises and descends due to buoyancy in accordance with the water level thereof so that the valve orifice 98 is opened and closed. The opening of the valve orifice enables the condensate in the valve chest 94 to be discharged and flows to the outlet port 92 through the outlet passage 99.
FIG. 8 is a sectional view substantially taken along a line A--A in FIG. 7, showing a condition that the condensate flows into the valve chest 94 from the inlet port 91. As understood from the FIGURE, the sectional configuration of an inlet for condensate which indicates an inlet portion, and a portion for connecting the inlet port to the valve chest is generally designed to be circular because of the connection to a pipe arrangement. When the condensate flows in this portion, therefore, the condensate flow is gathered at a portion close to a central portion of the inlet port, as shown in the FIGURE, then, becomes a thin water flow and flows down to the valve chest.
In the free float steam trap as mentioned above, the float valve is arranged in a free state in the valve chest, so that there originally arises such a defect that the float valve is liable to be vibrated. Therefore, when the condensate flow falls in a concentrated manner, as mentioned above, the float valve arranged at the destination of a fall of the condensate flow is significantly vibrated due to the action of the condensate flow. As a result, the contact between the float valve and the valve orifice is deteriorated, so that the leakage of fluid, especially, steam in the valve chest occurs.
When the condensate flows into the valve chest 94 from the inlet port 91 in a state as shown by an arrow X in FIG. 7, the condensate so exerts as to press the float valve 95 to the valve orifice 98, so that the float valve 95 is prevented from opening. As a result, there arises a problem that the discharge flow rate of the condensate is decreased.
On the other hand, when the condensate concentrically falls on the valve orifice side, the fluid in the vicinity of the valve orifice is brought into a turbulent state. Therefore, there arises such a problem that steam is liable to be involved in the fluid flowing out to the outlet port through the valve orifice.
Further, when the condensate falling in a concentrated manner is even slightly deflected from the center line of the float valve, namely, the axis of the valve orifice, the condensate flow so actuates as to push the float valve sideward. Consequently, the float valve is turned away from the valve orifice and the leakage of the fluid, especially, steam is induced.